I propose to evaluate the physiological and biochemical mechanisms responsible for the composition and formation of endolymph. Special attention will be paid to the role of diuretics in altering the electrolyte compositon of endolymph. The role of cyclic AMP in the formation of endolymph will be investigated by measuring the volume and the hydrostatic pressure of endolymph before and after the injection of drugs known to be stimulators of adenyl cyclase. In addition, it is planned to study the physiologic mechanisms which determine the penetration of drugs into the scala media.